Referring to FIG. 1, an existing large-diameter underwater pipe assembly for pumping seawater is composed of a plurality of interconnected pipes 101. Each pipe 101 includes a pipe body 101, and two connectors 102 respectively fixed to two opposite ends of the pipe body 101. By interconnecting the connectors 102 of two adjacent pipes 10, the length of the underwater pipe assembly can be prolonged. To facilitate the production, the pipe body 101 and the two connectors 102 are separately produced, after which the connectors 102 are welded to the two opposite ends of the pipe body 101.
However, a welded junction between the pipe body 101 and a corresponding one of the connectors 102 has an uneven shape, so that turbulence and resistance during pumping of the seawater are prone to occur. Furthermore, the structural strength of the welded junction between the pipe body 101 and the corresponding connector 102 is insufficient, so that it is susceptible to torque and pressure, thereby generating breakage.